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Astron. Astrophys. 351, 597-606 (1999)

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Do we really obtain reliable elemental abundances for supergiant stars?  *

V.V. Kovtyukh and S.M. Andrievsky

Department of Astronomy, Odessa State University, Shevchenko Park, 270014 Odessa, Ukraine (scan@deneb.odessa.ua)

Received 31 May 1999 / Accepted 31 August 1999

Abstract

We discuss the problems of standard spectroscopic analysis of intermediate mass supergiants and propose the usage of [FORMULA] lines for the microturbulent velocity and gravity determination, instead of [FORMULA] lines that are usually applied for this aim, but more affected by non-LTE effects.

With the example of [FORMULA] Cep (seven high-resolution and high signal-to-noise ratio spectra) we demonstrate that the proposed approach results in the following advantages:

  • it removes the long-standing problem of the discrepancy between the spectroscopic and physical gravities (based on the estimated stellar masses and radii), resulting in a complete agreement between these values;

  • it brings the abundances of some elements (among them carbon, nitrogen, oxygen) in accordance with the theoretically predicted atmospheric abundances for the supergiants of intermediate masses after the first dredge-up phase;

  • it allows us to keep an ionization balance of some elements observed in two ionizational stages together with the [FORMULA] balance.

Key words: stars: abundances – stars: individual: ffi Cep – stars: variables: Cepheids

* The Appendix is only available electronically with the On-Line publication.

Send offprint requests to: S.M. Andrievsky

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© European Southern Observatory (ESO) 1999

Online publication: November 3, 1999
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